In the prior art, the liner/piston or liner/plunger of a mud pump employs medium water to spray the interior bore surface of the liner so as to wash and cool the liner/piston or liner/plunger. However, those approaches cannot effectively lower the working temperature of the liner/piston or liner/plunger, and thus the service life of the liner/piston or liner/plunger is relatively short.
Documents relating to the above-mentioned prior art are, for example, CN Patent Application No. 200620078851.9, and CN Utility Patents No. ZL01252698.3 and ZL99257860.4.